Difficultly inflammable yarns, fibers and films of phosphorus containing polyesteramides and process for obtaining them

ABSTRACT

The invention concerns new difficultly inflammable polyesteramide yarns, fibers and films.

This is a division of application Ser. No. 472,155, filed May 22, 1974.

The present invention relates to yarns, fibers and films formed ofdifficultly inflammable, aromatic copolyesteramide polymers and a methodof preparing the same.

Linear polyesteramides which may be entirely aromatic, which are capableof being shaped into yarns, fibers and films, are known from FrenchPatent 1,474,377, but the ester groups and the amide groups aredistributed irregularly in the chain, and the products cited by way ofexample have melting points of between 150°C and 300°C.

It is known from French Patent 1,578,154 that aromatic polyamides can beobtained by reaction of a diacid with a diisocyanate. But it is notcontemplated that the diacid may have ester groups.

It is known from Belgian Patent 665,928 and from German Patent 922,255to couple polyesters of medium molecular weight having acid terminalgroups by means of a diisocyanate, but these processes are carried outunder conditions which lead to crosslinkings.

There have now been found -- and this constitutes the object of thepresent invention -- difficultly inflammable yarns, fibers, and filmsformed of aromatic copolyesteramide polymers obtained by extrudingfilaments by the known wet or dry processes or casting a film of asolution of the polymer, characterized by the fact that thesecopolyesteramides comprise linkages of the form --NH--Ar₁ --NH--, of theform --CO--Ar₂ --CO--, --OC--Ar₃ --Y_(a) --(Ar₄)_(b) --Y_(c) ---Ar₅--CO-- and in some cases ##STR1## in quantity of 4-30 mol %, preferably6-20 mol % with respect of acid units, Ar₁, Ar₂, Ar₃, Ar₄, Ar₅, Ar₆, Ar₇representing a divalent aromatic radical, Y being ##STR2## or--C--O--(CH₂)_(p) -- with p>1, and a, b and c being equal to 0 or 1, atleast one of the subscripts a or c being equal to 1, and M being analkali metal.

The invention also concerns a process for obtaining these yarns, fibersand films which comprises preparing the copolyesteramides by reaction,in substantially stoichiometric quantity, of at least one aromaticdiisocyanate and aromatic dicarboxylic acids at least one of saiddiacids containing one or two ester groups, which reaction may beconducted in the presence of 4-30 mol%, preferably 6-20 mol% withrespect of acid units of a polycondensation accelerating agent of theformula: ##STR3## in an anhydrous, aprotic, polar solvent medium, thetemperature being raised gradually to 200°C, and shaping the resultantsolution by extrusion by the wet or dry process or casting as a film.

In the process of the invention, the reagents are placed in solution ina temperature range of between 25°C and 130°C at ambient pressure or ina partial vacuum, the temperature being then increased during thereaction at a rate of between 0.2° and 5°C per minute and preferablybetween 0.5°, and 2°C per minute, up to at most 200°C and even 190°C inthe event that one is operating in the presence of the polycondensationaccelerating agent.

By substantially stoichiometric quantity within the meaning of thepresent invention there are meant molar ratios of carboxylic diacids todiisocyanates close to 1, and preferably between 0.90 and 1.20.

The diisocyanates included within the scope of the invention are of theformula: 0 = C = N -- Ar₁ -- = N = C = O.

the carboxylic diacids are of the formula:

    HOOC -- Ar.sub.2 -- COOH

or of the formula:

    HOOC -- Ar.sub.3 -- Y.sub.a (AR.sub.4).sub.b -- Y.sub.c -- Ar.sub.5 -- COOH

ar₁, Ar₂, Ar₃, Ar₄, Ar₅ representing divalent aromatic radicals withbonds either in meta or preferably in para position, such as ##SPC1##

where i = 0 or 1, X being ##STR4## with p ≧to 1, and preferably p = 1 or2, the subscripts a, b and c being equal to 0 or 1, at least one of thesubcripts a or c being equal to 1, at least one of the diacids being ofthe formula HOOC--Ar₃ --Y_(a) --(Ar₄)_(b) --Y_(c) --Ar₅ --COOH.

Among the diisocyanates which can be used within the scope of theinvention, mention may be made of toluylene diisocyanate (2-4 or themixtures of 2-4 and 2-6 isomers), diisocyanato 4-4' diphenyl propane,diisocyanato 4-4' diphenyl ether, and preferably diisocyanato 4-4'diphenyl methane.

Among the dicarboxylic acids there are used more particularlyterephthalic acid, isophthalic acid, and bis (4-carboxy benzyl)terephthalate. The proportion of diacid ester in the diacid/diacid estermixture may go up to close to 100 % but must be such that there are atleast 15 ester bonds per 100 total amide and ester bonds.

The molecular weight of the diacid ester will preferably be less than800.

When the polycondensation accelerating agent of phosphinic typeillustrated above is present, it should be present in a proportion of atleast 4 mols per 100 and preferably 6 mols per 100 mols of the totaldicarboxylic acids in order to be effective; it is preferred to use thepolycondensation accelerating agent in a proportion of at most 30 mols%, preferably at most 20 mols %, in order to avoid the formation ofchains having too much phosphorus, what would result in an increase ofsolubility of the polymer in the coagulating bath.

Among these agents, use is made more particularly of the monosodium saltof bis (carboxy-4 phenyl) phosphinic acid.

As solvent medium there is used an anhydrous, aprotic, polar organicsolvent, that is to say, one containing less than 600 ppm of water, andpreferably less than 200 ppm, such as:

linear or cyclic amides or phosphoramides such as dimethyl acetamide,hexamethyl phosphoryl triamide, tetramethyl urea, and preferablyN-methyl-2 pyrrolidone,

sulfones such as tetramethylene sulfone, etc.

The presence of an agent which permits the obtaining of bright fibers bywet-spinning, such as sodium dicarboxy 3-5 benzene sulfonate, isdesirable but not indispensable; it may be introduced at the same as thereagents and participates in the polycondensation reaction.

Fillers, pigments, optical brighteners and other products which areinert with respect to the reaction may also be added to the reactionmedium.

The reagents may be dissolved in the solvent simultaneously or insuccession or be dissolved separately and the solutions then mixed.

The concentration of the total reagents in the starting solution isbetween 5 and 50 %, and preferably between 15 and 40 %, expressed inweight of polymer obtained per 100 g of solution, that is to say, afterdeduction of the weight of CO₂ eliminated in the condensation betweenthe isocyanate and carbonyl groups.

In the first phase of the process, the different components areintroduced into a reactor provided with an agitator, a thermometricjacket, a reflux condenser and a dry nitrogen inlet, and the temperatureof which is between 20°C and 130°C.

A strong liberation of CO₂ takes place between 80 and 120°C andcontinues as the temperature of the reaction mixture rises at a rate ofbetween 0.2°C and 5°C per minute.

The total time of the operation is less than or equal to 15 hrs and moreparticularly of the order of 3 hrs., at the end of which time there isobtained a solution of a viscosity of between 200 and 5,000 poises,which may be obtained by dilution of the final mixture with thenecessary amount of solvent. During the entire operation, sufficientagitation is maintained to assure homogeneous heating, which isindispensable for good development of the reaction.

The inherent viscosity of the products obtained is greater than 0.5 andpreferably greater than 0.9.

In the second phase of the processing of the yarns, fibers and films inaccordance with the invention, the solution obtained in the first phaseis extruded by the wet or dry process, in accordance with knownprocedures, for instance by the process described in French Patent2,079,785.

In the case, for instance, of wet-spinning, the solution is extrudedthrough a spinneret immersed in a coagulation bath which comprises amixture of the solvent of the solution and water in proportions ofbetween 20 and 80 parts of solvent to 100 parts of bath; the gel formedundergoes stretching in air at a rate of about 3 times and which is thenwashed and wound up.

It may also be subjected to a continuous over-drawing at a rate of theorder of 1.5 times in a furnace brought to 250°C.

In the case of dry spinning the solution is extruded in a dry spinningcell in which a part of the solvent is eliminated so that the filamentsonly contain 50 to 150 % by weight of solvent at their exit from thecell; they are then washed at a temperature between about 60°C to 90°Cand stretched of about 3 times and eventually over-drawn of about 1.5times at 250°C in a furnace.

For the production of a film, the solution whose viscosity has beenlowered to about 100 poises by dilution is poured onto a glass platewhich is then brought to a temperature of between 80°C and 200°C in astove where a vacuum of the order of 1 mm of mercury is graduallyestablished; in a preferred embodiment, the film is first of all driedat 120°C under 650 mm Hg and then peeled from the plate and dried undervacuum between 150° and 200°C.

The yarns, fibers and films in accordance with the invention arecolorless or slightly colored; the copolyesteramides of which they areformed have a better thermal behavior than the polyesteramides known upto now, melting and carbonization taking place only above 300°C.Furthermore, when they contain chains derived from the phosphinicderivatives, they have no melting point, carbonization takes place onlyabove 380°C, and the post-incandescence phenomenon is non-existent.

They are of low inflammability and their mechanical properties are ofthe same order of magnitude as those of other inflammable syntheticyarns, fibers or films.

The yarns, fibers and films in accordance with the invention can be usedin all fields in which the property of non-inflammability is desired,such as upholstery, protective clothing, as well as in certainindustrial uses.

The following examples are given by way of illustration and not oflimitation. In these examples:

the absolute viscosity of the solutions is measured at 25°C by means ofan Epprecht Rheomat 15 apparatus,

the inherent viscosity η = Ln(t/t_(o))/C is measured at 25°C on an 0.5 gsolution of polymer in 100 ml of the solvent for the preparation of thepolymer, t and t_(o) being the flow times of the solution and solvent,and C the concentration of the solvent, expressed in weight per volume,

the differential thermal analysis curve is recorded on a Type 900apparatus of Du Pont Instrument, the sample, whether yarn or film, beingcompared with glass balls as a control,

the dynamometric characteristics of the fibers are determined afterconditioning at 22°C and relative humidity of 65%.

The tests for the determination of the degree of inflammability arecarried out on knits weighing about 90 g/m², desized, conditioned at22°C and a relative humidity of 65%.

They are:

the determination of the Oxygen Index (minimum concentration of oxygenfor combustion): there is concerned here ASTM Standard B 2863-70covering plastic test bars, modified and adapted to textile samples orfilms of dimensions of 5 × 16 cm mounted on a rectangular frame,

Test AATCC 34-1969 developed in the USA: the value given is the durationof burning after application of a flame fed by a gaseous mixture (H₂ +CH₄ + C₂ H₆ + CO) for 12 seconds and then withdrawn; thepost-incandescence is determined by the duration of the incandescenceafter extinction of the flame,

the gas-flame test: this is carried out on samples of 5 cm × 15 cm. Thesample is placed astride a horizontal rod and fastened thereon at one ofits ends; the flame of a Bunsen burner is applied for 5 seconds to thefree end of the sample; if extinction takes place upon withdrawal of theflame, the flame is again applied for 10 seconds and then for 20 secondsand then 30 seconds if necessary, and the duration of the successivecombusions is noted.

The post-incandescence which is the time of slow combustion of thematerial brought to red heat after the cessation of any flame isexpressed in seconds.

EXAMPLE 1

Into a 500-ml reactor provided with heating and agitating means and thetemperature of which has been brought to 80°C there are introduced:

33.60 g (0.132 mol) of diisocyanato 4-4'diphenyl ether

20.12 g (0.078 mol) of dicarboxy 4-4'diphenyl ether

13.02 g (0.078 mol) of di(p-carboxy benzyl) terephthalate

3.22 g (0.012 mol) of sodium dicarboxy 3-5 benzene sulfonate

139 g of N-methyl 2-pyrrolidone, the amount necessary to adjust theconcentration of the reagents to 30 g (of final polymer) in 100 g ofsolution.

The temperature is raised in 2 hours up to 180°C and stabilized at thisvalue for 30 minutes; a strong liberation of CO₂ takes place at thestart of the heating. After dilution with N-methyl 2-pyrrolidone, thereis obtained a collodion whose dry extract is 20.35%, expressed inweight, for 100 g of solution the viscosity of which is 65 poises. Theinherent viscosity of the polymer is 0.74.

From this solution there are produced, a film by casting, in constantthickness and then drying in a stove, first of all under ambientatmosphere and then under vacuum while the temperature rises up to160°C. Transparent, slightly yellowish films of different thicknessesare obtained.

These films exhibit good thermal behavior, as shown by a differentialthermal analysis curve which is uniform up to 450°C. Beyond that, theproduct carbonizes without melting.

The results of the inflammability tests are as follows:

                                      TABLE I                                     __________________________________________________________________________                   Height                                                                             Application                                                                          Time of                                                           de-  of the combus-                                                                            Post-incan                                               Oxygen                                                                            stroyed                                                                            flame in                                                                             tion in                                                                            descence in                                              index                                                                             in cm                                                                              sec    sec  sec                                           __________________________________________________________________________    Oxygen Index                                                                             25.5                                                               min. conc. of O.sub.2                                                         for combustion                                                                AATCC Test 34-1969                                                                           7.5         0    4                                             Gas-flame test       5     4    5                                                                 10     4    8                                                                 20     8    17                                                                30     0    15                                            __________________________________________________________________________

EXAMPLE 2

Into a 4-liter reactor provided with heating and agitating means and ata starting temperature of 120°C there are introduced:

302 g (1.19 mol) of 98.75% diisocyanato 4-4' diphenyl methane

316 g (0.835 mol) of 99.85% dicarboxy 4-4' diphenyl ether

96.4 g (0.22 mol) of 99% di(p-carboxy benzyl) terephthalate

11.8 g (0.044 mol) of sodium dicarboxy 3-5 benzene sulfonate

1.235 g of N-methyl 2-pyrrolidone.

The temperature of the reaction mass is raised gradually and at the endof 30 minutes is 135°C; at the same time a liberation of CO₂ takesplace; at the end of 1 hr. 40 min. it is 180°C and is stabilized at thisvalue for 30 minutes; after dilution with 325 ml of N-methyl pyrrolidoneand cooling, the viscosity of the final solution is 300 poises, the dryextract is 25.1 g per 100 g of solution and the inherent viscosity ofthe polymer is 0.76. This collodion is wet spun under the followingconditions: the spinneret comprising 64 apertures of 0.06 mm diameterand the temperature of which is 25°C is immersed in a coagulation bathformed of 52% N-methyl 2-pyrrolidone and 48% water (expressed asweight/weight) the temperature of which is 20°C; the solution comingfrom the spinneret after a path of 45 cm in said bath at a speed of 11m/min gives a coagulated yarn which is drawn in air at a ratio of 2.18 xand then washed with water on multiple-turn rolls, dried, and wound upat a speed of 24 m/min.

Its mechanical properties are:

    ______________________________________                                        Size                4.98 dtex                                                 Tenacity            8.52 g/tex                                                Elongation         13.3%                                                      ______________________________________                                    

This yarn can be over-drawn by passage through a tube at 250°C undernitrogen or air at a speed of 15 m/min, an over-draw ratio of 1.22 xbrings the mechanical properties to:

    ______________________________________                                        Size                3.35 dtex                                                 Tenacity           13.7 g/tex                                                 Elongation         12.3%                                                      ______________________________________                                    

The thermal properties of these yarns, in the form of desized knit of aweight of 90 g/m² are as follows:

The differential thermal analysis curve shows two endothermal peaks at353°C and 437°C; therefore no substantial physical transformation takesplace below 350°C.

The results of the inflammability tests are given in the followingtable:

                                      TABLE II                                    __________________________________________________________________________                    Height                                                                             Applica-                                                                            Duration                                                           de-  tion of                                                                             of com-                                                                            Post-incan-                                              Oxygen*                                                                            stroyed                                                                            the flame                                                                           bustion                                                                            descence                                                 Index                                                                              in cm                                                                              in sec                                                                              in sec                                                                             in sec                                        __________________________________________________________________________    Oxygen Index                                                                             23%                                                                AATCC Test 34-1969                                                                            14          8   0                                             Gas-flame test        5    42   0                                                                  10    20   0                                                                  20    26   0                                                                  30    18   0                                             __________________________________________________________________________     *min. conc. of oxygen for combustion                                     

EXAMPLE 3

The preparation of the monosodium salt of bis (carboxy-4-phenyl)phosphinic acid is carried out in the following manner:

Into a 20-liter round-bottom reactor there are introduced:

2448 g(8 mols) of bis (carboxy-4-phenyl) phosphinic acid

10 liters of N-methyl-2-pyrrolidone

Dissolving is effected with a deflocculating turbine in 10 minutes atroom temperature; a few impurities remain undissolved and are eliminatedby settling and filtration. The solution is then charged again into thereactor and, with vigorous agitation by means of the turbine, 310 g(7.76 mol) of soda and 2 liters of permutized water are added rapidlydrop by drop for 1 hour.

After 30 minutes, precipitation commences; the temperture of the mediumrises to 45°C. Cooling is effected with agitation. It is set asideovernight. It is them filtered on a Buchner funnel containing diatroseand flanelette. The filtrate is light yellow and the precipitate verywhite. It is dried for one day in a stove in a moist vacuum, graduallyincreasing the temperature up to 200°C.

The yield is 88.7% and the --COOH ratio 97.5% with respect totheoretical.

For the production of the polymer, there are then introduced into a500-ml reactor, provided with heating and agitating means, and thetemperature of which is brought to 120°C:

39.75 g (0.159 mol) of diisocyanato-4-4'-diphenyl methane

26.70 g (0.103 mol) of dicarboxy-4-4'-diphenyl ether

16.27 g (0.0375 mol) of di-(p-carboxy benzyl) terephthalate

2.95 g (0.009 mol) of monosodium salt of bis(carboxy-4-phenyl)phosphinic acid

164 g of N-methyl-2-pyrrolidone.

The temperature of the reaction medium is brought to 130°C within 30minutes and then held stable at this value for 40 minutes; a strongliberation of CO₂ takes place; thereupon the increase in temperature iscontinued so as to reach 180°C at the end of 1 hr. 50 min.; it ismaintained at this temperature for 1 hr. and at the same time there isgradually added a sufficient amount of N-methyl 2-pyrrolidone to obtaina final viscosity of the solution of 375 poises.

The dry extract of this solution them constitutes 17.65%, expressed byweight, and the inherent viscosity of the polymer is 1.02.

After a second dilution to lower the absolute viscosity of the solutionto 100 poises, films of an initial thickness of 0.40 mm are produced bypouring onto a glass plate; they are then dried under vacuum at 200°Cfor 5 hrs.

These slightly colored films have an Oxygen Index (min. conc. of oxygenfor combution of 25%). The behavior in the gas-flame test is shown inTable III.

                  TABLE III                                                       ______________________________________                                                     Duration                                                         Application  of com-      Post-incan-                                         of the flame bustion      descence                                            in sec       in sec       in sec                                              ______________________________________                                         5           2            1                                                   10           1            2                                                   20           1            0                                                   30           0            0                                                   ______________________________________                                    

This table shows in particular that there is no post-incandescence, andafter the test a large carbonized residue is found. The differentialthermal analysis curve is uniform up to 450°C; the product thereforedoes not melt below this temperature.

The mechanical properties and the resistance to chemical attack byorganic solvent, acid and base are summarized in Table IV. The drawnfilm exhibits excellent behavior with respect to these products.

                                      TABLE IV                                    __________________________________________________________________________                                    Gain (+)                                                                      or loss                                                           Gain (+)    (-) in                                        Condi-              or loss (-)                                                                          Elonga-                                                                            elonga-                                       tion of        Tenacity                                                                           of tenacity                                                                          tion tion                                          the film                                                                           Treatment g/mm.sup.2                                                                           %     %    %                                            __________________________________________________________________________    Non-                                                                          drawn           7,000       10.6                                              Drawn*          9,350       12.7                                              Drawn                                                                              10 min at 60°C                                                         in perchlor-                                                                  ethylene        + 4.27%    + 52%                                         Drawn                                                                              30 min in a 2%                                                                aqueous solu-                                                                 tion of H.sub.2 SO.sub.4                                                      (% by wt) at                                                                  the boiling point                                                                             + 4.27%    + 5.5%                                        Drawn                                                                              30 min in a 5%                                                                aqueous solu-                                                                 tion of NaOH                                                                  (% by wt) at                                                                  the boiling                                                                   point           - 4.27%    - 5.5%                                        __________________________________________________________________________    *The conditions for drawing are as follows:                                                temperature 270°C                                                      drawing speed 1 cm/min                                                        draw ratio 1.5 ×                                       

EXAMPLE 4

Into a 500-ml reactor similar to that of Example 3 there are introduced:

33.20 g (0.133 mol) of diisocyanato-4-4'-diphenyl methane

14.44 g (0.0565 mol) of dicarboxy-4-4'-diphenyl methane

24.48 g (0.0565 mol) of di- (p-carboxy benzyl) terephthalate

2.36 g (0.0072 mol) of monosodium salt of bis (carboxy-4-phenyl)phosphonic acid prepared in accordance with Example 3.

149 g of N-methyl-2-pyrrolidone, the amount necessary to adjust theconcentration of the resultant polymer to 30%.

The temperature is increased within 2 hours to 180°C. with a stay of 20minutes at 150°C, during which a strong liberation of CO₂ takes place,and then stabilized at this value for 30 minutes. To the resultantsolution there is added the amount of N-methyl 2-pyrrolidone necessaryto decrease the viscosity to 300 poises (the corresponding dry extractis 20.60%, expressed by weight), and then to 100 poises in a secondstage.

By pouring this last-mentioned solution onto a glass plate and thendrying in an oven at a temperature below 200°C there are obtained filmsof a thickness of between 60 and 100μ.

The polymer of which they are formed has an inherent viscosity of 1.26.

These films, which are slightly yellow in color, have the followingmechanical properties:

    ______________________________________                                        Ultimate strength   7,200 kg/mm.sup.2                                         Elongation          6.5%                                                      ______________________________________                                    

The differential thermal analysis curve, which is uniform up to 450°C,shows an absence of melting.

The inflammability and post-incandescence properties are shown in TableV.

                                      TABLE V                                     __________________________________________________________________________                   Height                                                                             Applica-                                                                            Duration                                                           de-  tion of                                                                             of com-                                                                            Post-incan-                                            "OXYGEN"*                                                                            stroyed                                                                            the flame                                                                           bustion                                                                            descence                                               index  in cm                                                                              in sec                                                                              in sec                                                                             in sec                                         __________________________________________________________________________    "CLOC" index                                                                          24.4                                                                  AATCC Test                                                                     34-1969       7          0    0                                              Gas-flame                                                                      test                5    2    0                                                                  10    3    0                                                                  20    0    0                                                                  30    0    0                                              __________________________________________________________________________     *Min. Conc. of Oxygen for Combustion                                     

This test shows that, for standard polycondensation conditions, there isobtained a product of particularly high inherent viscosity, having verygood non-flammability and post-incandescence characteristics.

EXAMPLE 5

Into an apparatus identical to that of Example 3 there are introduced:

32.37 g (0.128 mol) of diisocyanato-4-4'-diphenyl ether

20.74 g (0.0805 mol) dicarboxy-4-4'-diphenyl ether

13.02 g (0.03 mol) of di-(p-carboxy benzyl) terephthalate

3.15 g (0.0096 mol) of monosodium salt of bis (carboxy-4-phenyl)phosphinic acid as prepared in Example 3

137 g of N-methyl-2-pyrrolidone

The temperature is increased in 1 hr. 15 min. to 180°C; the liberationof CO₂ taking place above 100°C; at this stage of the operation there isadded an amount of N-methyl 2-pyrrolidone such that the concentration ofpolymer in the solution is 20% by weight; the total duration of theoperation is 2 hrs.

Upon another dilution there is obtained a solution having the followingproperties:

    ______________________________________                                        Absolute viscosity                                                                            200 poises                                                    Dry extract     15.90 g for 100 g of solution                                 Inherent viscosity                                                            of the polymer  0.95                                                          ______________________________________                                    

For the production of films, the absolute viscosity of this solution isreduced to 100 poises by a further addition of N-methyl 2-pyrrolidone.After pouring onto a glass plate and then drying in an oven, there areobtained transparent, practically uncolored films of an initialthickness of 0.70 mm, the properties of which are given in Table VI.

                  TABLE VI                                                        ______________________________________                                               Height de-                                                                            Application                                                                             Duration of                                                                             Post-incan-                                       stroyed in                                                                            of the flame                                                                            combustion                                                                              descence                                          cm      in sec    in sec    in sec                                     ______________________________________                                        Ultimate                                                                      strength                                                                      g/mm.sup.2 8.100                                                              Elongation                                                                    upon rup-                                                                     ture % 6.6                                                                    "Oxygen"*                                                                     Index 26.1                                                                    AATCC Test                                                                    34-1969  6                   0       0                                        Gas-flame           5        0       0                                        test               10        1       0                                                           20        0       0                                                           30        0       0                                        ______________________________________                                         *Min. Conc. of oxygen for combustion                                     

Furthermore, the differential thermal analysis curve does not show anyspecific point.

These results show that the presence of monosodium salt of bis(carboxy-4-phenyl) phosphinic acid in the reaction medium makes itpossible to obtain a polymer of high inherent viscosity and to produce apractially colorless film which is non-flammable and withoutpost-incandescence.

EXAMPLE 6

Into a 4-liter reactor provided with heating and agitating means andbrought to a temperature of 90°C there are introduced:

266 g (1.06 mol) of diisocyanato-4-4'-diphenyl methane of 98.75%

178.3 g (0.69 mol) of dicarboxy-4-4'-diphenyl ether

110.0 g (0.249 mol) of 98% di-(carboxy-4-benzyl) terephthalate

20 g (0.061 mol) of monosodium salt of bis (carboxy-4-phenyl) phosphinicacid as prepared in Example 3

1.255 g of N-methyl-2-pyrrolidone

The temperature is brought to 180°C in 2 hrs, with an intermediate stopof 30 minutes at 135°C; a strong liberation of CO₂ takes place primarilyduring the first hour; above 135°C, successive quantities of N-methyl2-pyrrolidone are added such that the viscosity does not increase above1,200 poises and is reduced at the end of the operation to 440 poises.

The dry extract of this solution is then 17.1% (by weight) and theinherent viscosity of the polymer is 1.12.

The solution is them wet-spun under the following conditions:

The spinneret, having 64 orifices of 0.05 mm, at a temperature of 90°C,is immersed in a coagulation bath formed of 52% N-methyl 2-pyrrolidoneand 48% water (expressed in weight/ weight) the temperature of which is20°C and the length 45 cm; the speed of spinning is 11 m/min.

The coagulated yarn then passes over water-washing rolls at a speed of23 m/min and is then drawn in air at a ratio of 2.10 X and sized.

The mechanical properties of the resultant yarn are:

    ______________________________________                                        Denier per filament    5.27 dtex                                              Tenacity              10.9 g/tex                                              Elongation            15.4 %                                                  ______________________________________                                    

This yarn can be over-drawn by passage at a speed of 15 m/min through atube brought to 250°C.

The over-draw ratio of 1.71 X makes it possible to bring the mechanicalproperties of the yarn to the following values:

    ______________________________________                                        Denier per filament    2.97 dtex                                              Tenacity              22.4 g/tex                                              Elongation            10.9 %                                                  ______________________________________                                    

The inflammability tests, carried out on knitted fabrics, give thefollowing values:

    ______________________________________                                        Oxygen Index    25.3                                                          AATCC Test 34-1969                                                                            Height destroyed 9 cm                                                         Duration of combustion 6 sec.                                 ______________________________________                                    

The inherent viscosity of 1.12 of the polymer and the absence ofpost-incandescence are two significant properties to be credited to thenew polymer of this example.

I claim:
 1. A difficulty inflammable filament, thread, fiber or film ofaromatic carbocyclic copolyester amide polymers consisting essentiallyofabout 40 to 55% of units of the formula --NH--Ar₁ --NH-- and about 60to 45% of acid units of the formula:

    --CO--Ar.sub.2 --CO--, --OC--Ar.sub.3 --Ya--(Ar.sub.4).sub.b --Yc--Ar.sub.5 --CO--

and ##EQU1## wherein Ar₁, Ar₂, Ar₃, Ar₄, Ar₅, Ar₆ and Ar₇ represent adivalent aromatic carbocyclic radical, Y is ##EQU2## with p>1, a, b andc being equal to 0 or 1, at least one of the subscripts a or c beingequal to 1, and M is an alkali metal, and the proportions of the units--CO--Ar₂ --CO--, --OC--Ar₃ --Ya--(Ar₄)_(b) --Yc--Ar₅ --CO-- and##EQU3## being such that there are at least 15 ester bonds per 100 totalamide and ester bonds and 4-30 mol. % of said phosphorus-containingunits.
 2. The filament, thread, fiber or film of claim 1 having amelting point above 300°C.
 3. The filament, thread, fiber or film ofclaim 1 wherein said phosphorus-containing units are present in anamount of 6-20 mol. %.
 4. A process for producing film or fiber formingcopolyesteramides according to claim 1, by reacting in substantiallystoichiometric quantity at least one (1) aromatic carbocyclicdiisocyanate and (2) aromatic carbocyclic dicarboxylic acids, at leastone of said acids containing one or two ester groups, with 4-30 mol. %,with respect to the acid units, of (3) a phosphorus-containingdicarboxylic acid of the formula ##STR5## in an inert, anhydrous,aprotic, polar solvent medium, the temperature being increased graduallyto 200°C.
 5. The process of claim 4, wherein said phosphorus-containingdicarboxylic acid is present in an amount of 6 to 20 mol. %.